Lindsay Davenport lost a set for the first time at this U.S. Open and also lost the euphoric feeling in the nerve-damaged toes of her left foot.

After playing pain-free in her first three matches, the throbbing in Davenport’s foot finally arose in yesterday’s third set. It wasn’t a surprise to Davenport, who’s come to realize the longer matches go, the more likely the two problem toes will become a factor.

It wasn’t enough of a factor yesterday, only because the 21-year-old, 19th-ranked Russian Nadia Petrova choked on her forehand enough times to give Davenport a 6-0, 6-7 (8-6), 6-2 victory at Ashe Stadium.

Quietly weaving a Hall-of-Fame career that she could solidify with a another Grand Slam title here, Davenport is an Open quarterfinalist for the seventh straight year. She took a cortisone shot before the Open began and is gulping Vioxx anti-flammatories that are commonnly used by NBA players.

“Towards the end, my foot was starting to get a little bit sore,” Davenport said. “I thought I’d just let her throw in the errors – and she was.”

On match point, Petrova fittingly put a forehand into the net – her 50th unforced error. Petrova, 21, who had never gotten past the second round in her prior three years at the Open, won the second-set tiebreaker 8-6 but that was the end of her highlights.

Now Davenport is a heavy favorite to make the semis, even with her foot problem. She gets a breather quarterfinal, facing 25th-ranked Argentine Paola Suarez, to whom she has never lost in five matches.

“It’s a great opportunity to get back to the semifinals,” said Davenport, the last woman not named Williams to win the Open. “Hopefully my foot will stay near the same that it has been because it’s definitely playable.” Playable against Petrova, but not top seed Kim Clijsters, whom undoubtedly she will meet in the semis.

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Suarez advanced to her first-ever quarterfinal, posting a thrilling three-set victory, 6-2, 3-6, 7-5 over Russian Elena Likhovtseva. Suarez rallied from a 5-2 third-set deficit. The final game included five deuces with the Russian being undone by a crucial double fault that gave Suarez match point. She prevailed after a long, booming baseline rally. The ending was so compelling CBS cut away from the Andy Roddick blowout . . . The newly married Davenport could become the first married Open titlist since Arantxa Sanchez-Vicario in 1994. Davenport was married to John Leach, brother of former player Rick Leach, in April. Asked if she does all the cooking, Davenport said, “There’s a lot of takeout involved in our relationship.”